﻿/* Smooth scrolling
Changes links that link to other parts of this page to scroll
smoothly to those links rather than jump to them directly, which
can be a little disorienting.

sil, http://www.kryogenix.org/

v1.0 2003-11-11
v1.1 2005-06-16 wrap it up in an object
*/

var ss = {
    fixAllLinks: function() {
        // Get a list of all links in the page
        var allLinks = document.getElementsByTagName('a');
        // Walk through the list
        for (var i = 0; i < allLinks.length; i++) {
            var lnk = allLinks[i];
            if ((lnk.href && lnk.href.indexOf('#') != -1) &&
          ((lnk.pathname == location.pathname) ||
	    ('/' + lnk.pathname == location.pathname)) &&
          (lnk.search == location.search)) {
                // If the link is internal to the page (begins in #)
                // then attach the smoothScroll function as an onclick
                // event handler
                ss.addEvent(lnk, 'click', ss.smoothScroll);
            }
        }
    },

    smoothScroll: function(e) {
        // This is an event handler; get the clicked on element,
        // in a cross-browser fashion
        if (window.event) {
            target = window.event.srcElement;
        } else if (e) {
            target = e.target;
        } else return;

        // Make sure that the target is an element, not a text node
        // within an element
        if (target.nodeName.toLowerCase() != 'a') {
            target = target.parentNode;
        }

        // Paranoia; check this is an A tag
        if (target.nodeName.toLowerCase() != 'a') return;

        // Find the <a name> tag corresponding to this href
        // First strip off the hash (first character)
        anchor = target.hash.substr(1);
        // Now loop all A tags until we find one with that name
        var allLinks = document.getElementsByTagName('a');
        var destinationLink = null;
        for (var i = 0; i < allLinks.length; i++) {
            var lnk = allLinks[i];
            if (lnk.name && (lnk.name == anchor)) {
                destinationLink = lnk;
                break;
            }
        }
        if (!destinationLink) destinationLink = document.getElementById(anchor);

        // If we didn't find a destination, give up and let the browser do
        // its thing
        if (!destinationLink) return true;

        // Find the destination's position
        var destx = destinationLink.offsetLeft;
        var desty = destinationLink.offsetTop;
        var thisNode = destinationLink;
        while (thisNode.offsetParent &&
          (thisNode.offsetParent != document.body)) {
            thisNode = thisNode.offsetParent;
            destx += thisNode.offsetLeft;
            desty += thisNode.offsetTop;
        }

        // Stop any current scrolling
        clearInterval(ss.INTERVAL);

        cypos = ss.getCurrentYPos();

        ss_stepsize = parseInt((desty - cypos) / ss.STEPS);
        ss.INTERVAL =
setInterval('ss.scrollWindow(' + ss_stepsize + ',' + desty + ',"' + anchor + '")', 10);

        // And stop the actual click happening
        if (window.event) {
            window.event.cancelBubble = true;
            window.event.returnValue = false;
        }
        if (e && e.preventDefault && e.stopPropagation) {
            e.preventDefault();
            e.stopPropagation();
        }
    },

    scrollWindow: function(scramount, dest, anchor) {
        wascypos = ss.getCurrentYPos();
        isAbove = (wascypos < dest);
        window.scrollTo(0, wascypos + scramount);
        iscypos = ss.getCurrentYPos();
        isAboveNow = (iscypos < dest);
        if ((isAbove != isAboveNow) || (wascypos == iscypos)) {
            // if we've just scrolled past the destination, or
            // we haven't moved from the last scroll (i.e., we're at the
            // bottom of the page) then scroll exactly to the link
            window.scrollTo(0, dest);
            // cancel the repeating timer
            clearInterval(ss.INTERVAL);
            // and jump to the link directly so the URL's right
            location.hash = anchor;
        }
    },

    getCurrentYPos: function() {
        if (document.body && document.body.scrollTop)
            return document.body.scrollTop;
        if (document.documentElement && document.documentElement.scrollTop)
            return document.documentElement.scrollTop;
        if (window.pageYOffset)
            return window.pageYOffset;
        return 0;
    },

    addEvent: function(elm, evType, fn, useCapture) {
        // addEvent and removeEvent
        // cross-browser event handling for IE5+,  NS6 and Mozilla
        // By Scott Andrew
        if (elm.addEventListener) {
            elm.addEventListener(evType, fn, useCapture);
            return true;
        } else if (elm.attachEvent) {
            var r = elm.attachEvent("on" + evType, fn);
            return r;
        } else {
            alert("Handler could not be removed");
        }
    }
}

ss.STEPS = 25;

ss.addEvent(window, "mouseover", ss.fixAllLinks);
